Sulfidation of pure Co, Y, and of a Co-15 wt.% Y alloy in H{sub 2}-H{sub 2}S mixtures at 600-800{degree}C
- Institute of Corrosion and Protection of Metals, Shenyang (China); and others
The corrosion of pure Co and Y and of a Co-15 wt.% Y alloy in H{sub 2}-H{sub 2}S mixtures providing a sulfur pressure of 10{sup {minus}8} atm. at 600-800{degrees}C and also of 10{sup {minus}7} atm. at 800{degrees}C was studied to examine the effect of yttrium on the sulfidation resistance of pure cobalt. The alloy was nearly single-phase, containing mostly the intermetallic compound Co{sub 17}Y{sub 2} plus a small amount of cobalt solid-solution. For all conditions except for 800{degrees}C under 10{sup {minus}8} atm. S{sub 2}, the addition of yttrium reduced the sulfidation rate of cobalt, even though the formation of a continuous protective external layer of a pure yttrium compound was never achieved. Finally, when the gas-phase sulfur pressure was above the dissociation of cobalt sulfide the corrosion rate of yttrium was significantly lower than that of Co-15Y. The internal sulfidation of Y in Co-15Y was not associated with depletion of Y in the alloy. This diffusionless kind of internal attack is typical of binary A-B alloys presenting a very small solubility of the most-reactive component B in the base metal A, which restricts severely the flux of B from the alloy toward the alloy-scale interface.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 563588
- Journal Information:
- Oxidation of Metals, Journal Name: Oxidation of Metals Journal Issue: 3-4 Vol. 48; ISSN OXMEAF; ISSN 0030-770X
- Country of Publication:
- United States
- Language:
- English
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